Q: The ground under my avocado tree dries quickly. I’m thinking I should mulch it, but with what? — Lawrence Olsen, Los Angeles, CA
A: Mulching is the best thing you can do for your avocado, which has shallow roots and likes moist soil. The best mulch is yard waste (a blend of leaves and grass clippings, ideally shredded or partially composted). Otherwise, use composted bark or bark chips, available at most nurseries and garden centers. Apply the material 2 to 4 inches deep around the tree and out to the edge of the leaf canopy—even beyond if you can. Keep a 6-inch band around the trunk free of mulch. You will still need to irrigate the tree to keep it productive. And you probably should replenish the mulch every six months or so, as it decays.